Export MobiledocParser and utils functions to support extensibility

[lukemelia]

Our use case for these additional exports is as follows:

MobiledocParser: we use it in a "cleaning" service that processes mobiledoc before saving to remove cards that have been added but not configured and so are effectively empty and should be removed.

parsePostFromHTML: we use it to let users convert older HTML content to mobiledoc, and in our tests to allow succinct creation of mobiledoc from HTML

parsePostFromText: we use it to convert text from a CSV import into mobiledoc for further editing in our UI

detect: we use it to find link markups in a mobiledoc to facilitate selection expansion when replacing a link

[lukemelia]

Looks like the build failure here is related to SauceLabs credentials.

[gpoitch]

Use cases sound good.

I believe you can do these with public api:

MobiledocParser:

const post = new Editor({ mobiledoc: { version: '0.3.2', atoms: [], cards: [], markups: [['strong']], sections: [[1, 'p', [[0, [], 0, 'Foo '], [0, [0], 1, 'bar'],],],],},}).loadPost()

parsePostFromHTML:

const post = new Editor({ html: '<p>Foo <b>bar</b></p>' }).loadPost()

parsePostFromText: could add a text option and perform like above.

detect: seems like a pretty basic utility to just copy